Within a rotational optical arrangement, an electromagnetic (EM) energy path is defined so that the EM energy is incident upon only a portion of the rotational optical arrangement. A component of the EM energy proceeds away from the optical arrangement. The composition of the EM energy component proceeding from the arrangement is dependent upon a characteristic of the portion of the arrangement upon which the EM energy is incident. Typically, such arrangements are utilized to either reflect or transmit EM energy in a manner that differs according to rotational position of the arrangement.
Although such arrangements find application at various portions of the EM energy spectrum, the most common use is for the light portion of the EM spectrum. As such, the discussion herein is directed primarily to the application to light. For use with light, rotational optical arrangements are utilized for many applications. In one example, the optical arrangement is an optical wheel that has a plurality of optical filters. In a specific example, the optical arrangement includes a plurality of deflection mirror components that are associated with the optical filtering.
Each filter permits progress of a certain optical characteristic, such as a certain color portion of the spectrum. During rotation of the optical wheel, the different optical filters are sequentially brought into a light path. These optical wheels are often used to generate a multicolor image (e.g., a video image) for a display device or system. During operation, the optical wheel is rotated very rapidly such that the optical filters are rapidly, sequentially brought into the light path. For the color wheel, the rapid rotation provides for rapid color change.
In another example, the optical filters may provide differing degrees of polarization. Still further, any other optical characteristics may be employed within the rotational optical arrangement (e.g., holography). As mentioned, the optical arrangement may provide for either reflection or transmission of the light characteristics associated with specific optical filters. Again, all of the possible examples of such a rotational optical arrangement rely upon rotation to sequentially bring the optical filters (e.g., reflective/transmissive, color/polarization, etc.) into the light path.
The path of the incident light proceeding toward the optical arrangement is generally controlled by the positioning and targeting (i.e., focusing) associated with the light source. However, the light component(s) proceeding from the optical arrangement is dependent upon positioning, orientation, etc. of the optical arrangement. Typically, in order to have suitable usability of the light component(s) proceeding from the rotational optical arrangement, the proceeding light component(s) must have precise orientation (e.g., direction). For example, a rotational optical arrangement may be utilized within a system that must be able to produce a high quality image. Associated with such high quality image production, optical changes are executed very rapidly. As such, the optical filters of the rotational optical arrangement are moved (i.e., rotated) though the path of the light beam at a very high speed. Rotation within the optical arrangement must accordingly be associate with a well-centered and balanced drive (e.g., a motor). High accuracy of radial concentricity is desirable in order to achieve a long operational life. Further, for good image quality, radial offset and skew offset of the rotating optical filters should be minimized. Such minimization will promote a well-defined sequence and accurate synchronization.
FIG. 1 is a side view of an example of a rotational optical arrangement 10 that includes a rotational disk 12 and a motor platform 14. The disk 12 has a series of optical components (e.g., filters) spaced about its periphery. The motor platform 14 has a center rotational axis 16. The disk 12 is affixed to the motor platform 14 such that the motor platform 14 rotates the disk. The rotation of the disk 12 causes the sequential movement of the optical components on the disk relative to as incident beam of light (not shown).
The disk 12 includes an upper surface 18 with a center that provides reflection of a component of the incident beam based upon optical properties of the respective optical filtering component upon which the beam of light is incident. An interface normal direction 20 extends perpendicular to the plane of the upper surface 18, and is located in the center of the upper surface 18. In a perfect situation, the interface normal direction 20 is aligned with the center axis 16 of the motor platform 14. Specifically, the interface normal direction 20 is not spaced. radially from the center axis 16. Also, the interface normal direction 20 does not have any angle of inclination (i.e., skew) with regard to the center axis 16. In other words, the interface normal direction 20 is exactly coincident with the center axis 16.
However, during attachment of the disk 12 onto the motor platform 14 mounting errors can occur that result in the interface normal direction 20 not being perfectly coincident with center axis 16. FIG. 2 shows one example of the optical arrangement 10′ with such an error. Within this example, the disk 12′ is radially offset toward one direction (e.g., toward the right as shown in FIG. 2) relative to the motor platform 14′. This radial offset results in a radial displacement “d” of the interface normal direction 20′ from the center axis 16′. Of course, it is to be appreciated that the displacement “d” as shown in FIG. 2 may be greatly exaggerated. However, the illustration of FIG. 2 is useful to indicate the concept of radial offset misalignment. Further, depending upon the precision needed, even a small amount of radial offset (displacement “d”) may cause problems within the rotational optical arrangement 10′.
FIG. 3. illustrates skew between the disk 12″ and the motor platform 14″ of the optical arrangement 10″. Specifically, the interface normal direction 20″ is at an angle “α” relative to the center axis 16″. Similar to FIG. 2, the error in the mounting, as shown by α within FIG. 3, may be greatly exaggerated. However, the indication of the occurrence of the angle “α” between the interface normal direction 20″ and the center axis 16″ is useful to indicate the error that can occur. Further, even the smallest skew angle “α” may cause a degradation in performance of the optical arrangement 10″.
The radial offset “d” and the skew “α,” as shown within FIGS. 2 and 3, may occur simultaneously. Further, the occurrence of one of radial offset or skew may occur upon efforts to correct the other of the radial offset or skew. This is due to the fact in order to try to produce the optical arrangement 10 as shown in FIG. 1, the disk 12 is mounted onto the motor platform 14 via a generally one step affixing procedure. Typically, the disk 12 is attached to the motor platform 14 via the use of adhesive with the disk then being manipulated relative to the motor platform to try and simultaneously correct radial offset and skew.